1. Field of the Invention
The present invention relates to a multiplexing technology for processing fixed-length cell data such as an ATM cell, etc. and time-division data in time-division multiplexing communications when these data coexist.
2. Description of the Related Art
Recently, as a private branch LAN, etc. becomes more and more popular with Internet access, intra-net, and groupware, etc. implemented, a WAN communications device is required to integrate and accommodate a conventional voice trunk line and a low-speed data transmission line with a LAN traffic, and to dynamically secure a relay bandwidth of a LAN traffic having a high burst function.
An ATM multiplexing technology for transmitting each piece of data by logically multiplexing fixed-length cell data has been studied as a technology of dynamically using a relay bandwidth mainly for use in a broadband field. Recently, this ATM multiplexing technology has been applied to a narrowband field.
In this case, an existing STM (synchronous transfer mode) exclusive line capable of mainly using a multiplexing access service, etc. is used as a trunk line. In transmitting existing low-rate media information, a delay occurring when data is put in a cell has a large influence on the communications quality. Consequently, there is a need for a multiplexing device capable of integrating an ATM multiplexing technology for efficient transmission and flexible operation under traffic fluctuations into a TDM (time-division multiplexing) technology for exactly guaranteeing the quality of a circuit.
FIG. 1 shows the configuration of the first conventional technology of a multiplexing device. With this multiplexing device, the data communications between terminal ports 103, between a terminal port 103 and the line port 104, or between line ports 104 (one of the ports is not shown in the figure) are made through an ATM switch (ATM-SW) 101 and an ATM bus 102 using multiplexed ATM cells.
Therefore, to support the function of utilizing the TDM multiplexing technology, a package for realizing the TDM function is independently developed and implemented such that a realized TDM process can be performed within the package.
FIG. 2 shows the configuration of the second conventional technology of a multiplexing device. With this multiplexing device, a TDM multiplexing unit 201 is completely separate in function from an ATM multiplexing unit 202, and the data communications between these units are established through a cell assembling/disassembling unit (CLAD) 211 in the ATM multiplexing unit 202 and a CLAD interface unit (CLAD IF) 207 in the TDM multiplexing unit 201.
A terminal port 205 in the TDM multiplexing unit 201 accommodates a TDM terminal for TDM communications. The TDM multiplexing unit 201 terminates the STM exclusive line for TDM transmission. The data communications between these ports are established through a TDM switch (TDM-SW) 203 and a TDM bus 204 using multiplexed time-division data.
On the other hand, a line port 210 in the ATM multiplexing unit 202 terminates an ATM exclusive line. A terminal port not shown in FIG. 2 accommodates an ATM terminal which establishes ATM communications. The data communications between these ports are established through an ATM-SW 208 and an ATM bus 209 using a multiplexed ATM cell.
The CLAD IF 207 in the TDM multiplexing unit 201 has the function of multiplexing/demultiplexing time-division data to be put in a cell, and the function of processing the multiplexed time-division data as a frame or multi-frames. The CLAD IF 207 in the TDM multiplexing unit 201 and the CLAD 211 in the ATM multiplexing unit 202 are connected by a TDM multiplexing line 212 in which a frame or multi-frames are put. Then, the CLAD 211 in the ATM multiplexing unit 202 puts in a cell the time-division data which has been multiplexed and put in a frame or multi-frames. It also has the function of converting an ATM cell into time-division data.
Described below is the first case of conventional ways for effective use of resources,in which an ATM cell i""s transmitted using an arbitrary time slot of an STM exclusive line through an existing STM exclusive line available mainly for multiplexed access services, etc., not through a large transmission-capacity ATM exclusive line as a trunk line of the ATM cell.
To realize the first case with the configuration according to the first conventional technology shown in FIG. 1, it is necessary to realize within the line port 104 the function of terminating the time-division multiplexed data transmitted through the STM exclusive line, and the function of mapping an ATM cell input through. the ATM bus 102 to an arbitrary time slot in the STM exclusive line, and conversely retrieving and outputting to the ATM bus 102 the ATM cell mapped to the optional time slot.
Therefore, if the number of groups of the time slots to which the ATM cells are mapped becomes large, then it is necessary to correspondingly extend the above described conversion function in the line port 104. Therefore, it is hard to realize a flexible line port 104, and the number of extended ports is limited.
On the other hand, the first case with the configuration according to the second conventional technology shown in FIG. 2 can be realized as follows. That is, the line port 210 for terminating time-division data is extended in the ATM multiplexing unit 202 corresponding to each time slot to which ATM cells are mapped. The line port 210 is connected to the terminal port 205 provided in the TDM multiplexing unit 201. The ATM cell transmitted to and from the line port 210 in the ATM multiplexing unit 202 through the terminal port 205 is mapped to predetermined one or more time slots in the STM exclusive line terminated by a line port 206.
In this case, when the number of time slots to which the ATM cell is to be mapped increases in the STM exclusive line which terminates the line port 206, only the line port 210 in the ATM multiplexing unit 202 and the terminal port 205 in the TDM multiplexing unit 201 have to be correspondingly extended. Therefore, with the configuration according to the A second conventional technology, a flexible operation can be realized to some extent when the number of time slots to which an ATM is to be mapped increases.
However, with the configuration according to the second conventional technology, it is necessary to simultaneously extend the line port 210 in the ATM multiplexing unit 202 and the terminal port 205 in the TDM multiplexing unit 201, thereby causing the problem that the number of packages increases.
Described below is the second case in which an ATM cell contains existing low-rate media data such as modem data, FAX data, etc.
To include low-rate media data in an ATM cell, a CLAD is required to assemble and disassemble the ATM cell. In this case, the low-rate media data has to be mapped to an ATM cell without padding dummy data after the low-rate media data is time-division multiplexed, in order to suppress the delay in putting data in a cell and prevent the reduction in multiplexing efficiency. Furthermore, the function of arbitrarily relay the multiplexed low-rate media data in units of that media data is also required.
To realize the second case with the configuration according to the first conventional technology shown in FIG. 1, the terminal port 103 is designed to contain a plurality of terminals which communicate low-rate media data. In the terminal port 103, the low-rate media data is time-division multiplexed/demultiplexed in units of plural terminals. The corresponding time-division multiplexed data should be mapped to an ATM cell.
As a result, according to the first conventional technology, the low-rate media data which can be time-division multiplexed is limited to the data which can be communicated by a terminal accommodated by the terminal port 103. Accordingly, there is the problem that it is difficult to realize a flexible terminal port 103, and the time of time-division-multiplexing of low-rate media data is limited.
Furthermore, according to the first conventional technology, it is not possible to realize the function of arbitrarily relay the low-rate media data in units of that media data.
On the other hand, the second case can be realized with the configuration according to the second conventional technology shown in FIG. 2 in the following steps. For example, low-rate media data for each terminal port 103 is time-division multiplexed/demultiplexed in the CLAD IF 207 in the TDM multiplexing unit 201. Then, the corresponding time-division multiplexed data is mapped to the ATM cell in the CLAD 211 in the ATM multiplexing unit 202.
However, with the configuration according to the second conventional technology, the TDM multiplexing unit 201 is completely separate in function from the ATM multiplexing unit 202, and it is difficult to collectively control the CLAD IF 207 and the CLAD 211. Therefore, it is necessary to communicate the control information for mapping time-division multiplexed data to an ATM cell between the CLAD IF 207 and the CLAD 211. Accordingly, firmware, etc. is required to assign the control information to the TDM multiplexing line 212 and communicate the control information in each of the TDM multiplexing unit 201 and the ATM multiplexing unit 202, thereby causing the problem that the entire system is costly, the control process to be realized is complicated, and the system performance becomes deteriorated. With the configuration according to the second conventional technology, the following control sequence is required to realize the function of arbitrarily relaying multiplexed low-rate media data in units of that media data. That is, an ATM cell to be relayed is converted into time-division multiplexed data by the CLAD 211 in the ATM multiplexing unit 202 and transmitted to the CLAD IF 207 in the TDM multiplexing unit 201, and the time-division data is reassigned. Then, the resultant new time-division multiplexed data is transmitted again to the CLAD 211 in the ATM multiplexing unit 202 and converted into an ATM cell. In this case, since further complicated control information should be communicated between the CLAD IF 207 and the CLAD 211, the necessary function becomes too complicated.
Described below is the third case in which the voice data communicated through a terminal port (digital trunk) with a private branch exchange (PBX) is stored in an ATM cell.
In this third case, original voice data is compressed and encoded for each voice channel, and then the compressed and encoded voice data is put in a cell. Conversely, the function of retrieving the compressed and encoded voice data from an ATM cell, and then decoding the original voice data is required.
To realize the third case with the configuration according to the first conventional technology shown in FIG. 1, it is necessary to provide the terminal port 103 with a CODEC circuit for compressing, encoding and decoding voice data. The scale of the provided CODEC circuit depends on the number of the voice channels to be processed by the terminal port 103. Accordingly, there is the problem that it is difficult with this configuration to realize a flexible terminal port 103.
On the other hand, the third case is realized with the configuration according to the second conventional technology shown in FIG. 2 by implementing a CODEC circuit in the TDM multiplexing unit 201, and putting the compressed and encoded voice data in a cell with the CLAD 211 in the ATM multiplexing unit 202.
However, with the configuration according to the second; conventional technology, as in the above described second case, control information for mapping the compressed and encoded time-division multiplexed voice data to an ATM cell should be communicated between the CODEC circuit in the TDM multiplexing unit 201 and the CLAD 211 in the ATM multiplexing unit 202. Accordingly, firmware, etc. is required to assign the control information to the TDM multiplexing line 212 and communicate the control information to each of the TDM multiplexing unit 201 and the ATM multiplexing unit 202, thereby causing the problem that the entire system is costly, the control process to be realized is complicated, and the system performance becomes deteriorated.
In compressing and encoding voice data, a no-voice period is detected to stop transmitting voice data in that period. However, it is also necessary to notify the CLAD 211 from the CODEC circuit in the TDM multiplexing unit 201 of the no-voice detection information for stopping putting data in a cell in the no-voice period detected in the CODEC circuit. This also implies complicated control.
Finally described is the fourth case in which, if it is requested to prevent media data from being deteriorated in communications quality due to the delay in putting data in a cell, due to the discard of cells, etc., then the media data is time-division multiplexed (TDM multiplexed), the high-burst LAN data, etc. is time-division-multiplexed into predetermined one or more time slots after being ATM-multiplexed, and the data is transmitted in a mixed manner through one STM exclusive line.
When the fourth case is realized with the configuration according to the first conventional technology shown in FIG. 1, the communications data of the terminal port 103 and the line port 104 are necessarily put in cells. Therefore, it is not possible to realize the fourth case with the configuration according to the first conventional technology.
On the other hand, with the configuration according to the second conventional technology, the fourth case can be realized as in the first case, but has the same problem as the first case.
There also is the problem that, in assigning each time slot in the STM exclusive line, management is required in both the TDM multiplexing unit 201 and ATM multiplexing unit 202, thereby requiring complicated control.
As described above, with the configuration according to the first conventional technology shown in FIG. 1, there is the problem that it is hard, or it is possible but with limitations in specification to realize the functions of the first through fourth cases. Furthermore, there also is the problem that it is possible to realize the functions but an exclusive package has to be developed for each function, thereby enlarging the development scale and cost.
On the other hand, with the configuration according to the second conventional technology shown in FIG. 2, it is possible to realize the functions of the above described first through fourth cases, but it is necessary to develop a terminal port, a line port, a CLAD IF, a CLAD, etc. independently for the TDM multiplexing unit 201 and the ATM multiplexing unit 202. As a result, the development scale and cost are enlarged. There also is the problem that the control process for collectively managing the TDM multiplexing unit 201 and the ATM multiplexing unit 202 has become too complicated to be successfully performed.
The present invention has been developed based on the above described background, and aims at easily and collectively managing the TDM-multiplexed portion and the ATM-multiplexed portion by allowing the TDM system and the ATM system to efficiently coexist in a small scale and at a low cost.
The present invention is based on the fixed-length cell data/time-division data hybrid multiplexing device capable of processing fixed-length cell data such as an ATM cell, etc. and time-division data stored in a mixed manner.
First, an asynchronous transfer mode bus (ATM bus 304) asynchronously transfers fixed length cell data (ATM cells).
The time-division multiplexing bus (TDM bus 302) transfers multiplexed time-division data.
A control bus (control bus 402) transfers control data.
A time division multiplexing switch (TDM-SW 301) is connected to a time-division multiplexing bus, and switches the time-division data multiplexed in the time-division multiplexing bus.
An asynchronous transfer mode switch (ATM-SW 303) is connected to an asynchronous transfer mode bus and switches fixed-length cell data in the asynchronous transfer mode bus.
One or more time-division multiplexing bus slots (TDM bus slot 310) can implement one of the various process package devices (various process boards 308) for processing time-division data or fixed-length cell data, and are connected to a time-division multiplexing bus.
One or more asynchronous transfer mode bus slot (ATM bus slot 311) can implement one of the above described various process package devices, and are connected to an asynchronous transfer mode bus.
One or more control bus slots (control bus slot 403) can implement one of the above described various process package devices and are connected to a control bus.
With the configuration according to the above described invention, the time-division multiplexing bus slot can be provided with any of a hybrid line port package device (line port 309) containing the functions for terminating a time-division multiplexing line for transmitting a multiplexed time slot and mapping the fixed length cell data to the time slot; the hybrid process package device (various process boards 308), simultaneously connected to an asynchronous transfer mode bus slot, for mapping the time slot in the time-division multiplexing bus to the fixed-length cell data in the asynchronous transfer mode bus; a first terminal port package device (terminal port 305 or 307) for accommodating various terminals; a time-division multiplexing line port package device (line port 309) for terminating a time-division multiplexing line for transmitting multiplexed time division data; and a time-division multiplexing data processing package device (various process boards 308) for processing time-division data input through a time-division multiplexing bus and outputting it through the time-division multiplexing bus.
The asynchronous transfer mode bus slot can be provided with any of a hybrid line port package device (line port 309); a hybrid process package device (various process boards 308) simultaneously connected to the time-division multiplexing bus slot; a second terminal port package device (terminal port 306 or 307) for accommodating various terminals; an asynchronous transfer mode line port package device (line port 309) for terminating the asynchronous transfer mode line for transmitting fixed-length cell data (line port 309); and a fixed-length cell process package device (various process boards 308) for processing fixed-length cell data input through an asynchronous transfer mode bus, and outputting the processed data through the asynchronous transfer mode bus.
With the above described configuration according to the present invention, a terminal port for terminating a time-division multiplexing, a terminal port for terminating an asynchronous transfer mode, a terminal port for terminating both time-division multiplexing and asynchronous transfer mode, etc. can be implemented as an optional combination among them in the same unit by including a time-division multiplexing bus slot, an asynchronous transfer mode bus slot, and a control bus slot.
Furthermore, with the configuration according to the present invention, the same unit can be used when the communications type realized by the unit is changed by connecting a line port package device to the purpose to one or both of the time-division multiplexing bus slot and the asynchronous transfer mode bus slot.
With the configuration according to the present invention, the function realized by the hybrid multiplexing device according to the present invention can be flexibly extended by only connecting one of various process packages suited to the purpose to one or both of the time-division multiplexing bus slot and the asynchronous transfer mode bus slot.
Furthermore, with the configuration according to the present invention, collective control can be realized on all of various process package devices through a control bus slot, thereby solving the problem of the conventional technology that the control process is necessarily complicated.
With the above described configuration, the hybrid line port package device (309) for realizing various process package devices can be designed as a combination of a physical layer termination circuit, a transmission conversions layer termination circuit, and a multiplexing/demultiplexing circuit.
First, a physical layer terminating circuit (501) terminates the physical layer of a time-division multiplexing line (STM exclusive line).
Next, a transmission convergence layer terminating circuit (TC layer terminating circuit 502) can be connected to an asynchronous transfer mode bus slot, and the fixed-length cell data input through the asynchronous transfer mode bus is mapped to predetermined one or more time slots in a time-division multiplexing line. Conversely, the TC layer terminating circuit 502 retrieves the fixed-length cell data mapped to the time slots, and outputs the data to an asynchronous transfer mode bus.
Then, a multiplexing/demultiplexing circuit (503) can be connected to the transmission convergence layer terminating circuit, and also to the time-division multiplexing bus slot. Then, it multiplexes the time slot input from the transmission convergence layer terminating circuit and the time slot input from the time-division multiplexing bus, and outputs the result to the time-division multiplexing line through the physical layer terminating circuit. Conversely, the multiplexing/demultiplexing circuit 503 demultiplexes the time-division data output to the transmission convergence layer terminating circuit and the time-division data output to the time-division multiplexing bus from the time-division multiplexed data input from the time-division multiplexing line through the physical layer terminating circuit. A fixed-length cell corresponding to a transmission path can be mapped to a time-division multiplexing line only by connecting the hybrid line port package device having the above described configuration to the asynchronous transfer mode bus slot and the time-division multiplexing bus slot (and control bus slot). In the time-division multiplexing line, a time slot for transmitting a fixed-length cell and a time slot for transmitting time-division data can be kept in a mixed manner.
The above described configuration according to the present invention can be designed as a plural port TC layer process package device (505) which realizes one of various process package devices, and can comprise the following transmission convergence layer terminating circuit and multiplexing/demultiplexing circuit.
First, one or more transmission convergence layer terminating circuits (TC layer terminating circuit 506) can be connected to an asynchronous transfer mode bus slot. It maps the fixed-length cell data input from the asynchronous transfer mode bus to one or more predetermined time slots in the time-division multiplexing line. Conversely, it retrieves the fixed-length cell data mapped to the time slots and outputs the data to the asynchronous transfer mode bus.
A multiplexing/demultiplexing circuit (507) is connected to each transmission convergence layer terminating circuit, and also to a time-division multiplexing bus slot. It multiplexes and outputs to the time-division multiplexing bus the time slot to which fixed-length cell data is mapped after being input from each transmission convergence layer terminating circuit. Conversely, the multiplexing/demultiplexing circuit (507) demultiplexes the time slot, to which each fixed-length cell data output to each transmission convergence layer terminating circuit is mapped, from the time slot to which the fixed-length cell data input from the time-division multiplexing bus is mapped.
When the communications path of the transmitted fixed-length cell data as time slots to which the fixed-length cell data is mapped in the time-division multiplexing line is expanded, the fixed-length cell data corresponding to a plurality of paths can be mapped to the time-division data in the specified time slot in the time-division multiplexing line only by connecting the hybrid process package device. having the above described configuration of a necessary scale to an asynchronous transfer mode bus slot and a time-division multiplexing bus slot (and control bus slot).
The above described configuration according to the present invention can be designed as a low-speed data TDM multiplexing and CLAD package device (701) which realizes one of various process package devices, and can comprise the following multiplexing/demultiplexing circuit and cell assembly/disassembly layer terminating circuit.
First, the multiplexing/demultiplexing circuit (TDM multiplexing circuit 702) can be connected to a time-division multiplexing bus slot, whereby it multiplexes and outputs plural pieces of low rate media data (low-rate data) as one or more pieces of time-division data. Conversely, the multiplexing/demultiplexing circuit demultiplexes plural pieces of low-rate media data from one or more pieces of input time-division data, and outputs the resultant data to the time-division multiplexing bus.
Then, the cell assembly/disassembly layer terminating circuit (SAR layer terminating circuit 703) can be connected to an asynchronous transfer mode bus slot, sequentially converts one or more pieces of time-division data input from the multiplexing/demultiplexing circuit into a fixed-length cell, and outputs the cell to the asynchronous transfer mode bus. Conversely, it sequentially converts a fixed-length cell input through the asynchronous transfer mode bus into one or more pieces of time-division data, and outputs the data to the multiplexing/demultiplexing circuit.
Low-rate media data can be time-division multiplexed and mapped to a fixed-length cell only by connecting the hybrid process package device having the above described configuration of a necessary scale to an asynchronous transfer mode bus slot and a time-division multiplexing bus slot (and control bus slot).
The above described configuration according to the present invention can be designed as a hybrid process package device (1101) which realizes one of various process package devices, and can comprise the following voice compressing coder-decoder circuit and cell assembly/disassembly layer terminating circuit.
First, a voice compressing coder-decoder circuit (CODEC. 1102) can be connected to a time-division multiplexing bus slot, compresses, encodes, and outputs the voice data input from the time-division multiplexing bus. Conversely, it decodes the input compressed-encoded voice data, and outputs the data to the time-division multiplexing bus.
Then, a cell assembly/disassembly layer terminating circuit (SAR layer terminating circuit 1103) can be connected to an asynchronous transfer mode bus slot, sequentially converts the compressed and encoded voice data input from the voice compressing coder-decoder circuit into a fixed-length cell, and outputs the cell to the asynchronous transfer mode bus. Conversely, the SAR layer terminating circuit 1103 sequentially converts the fixed-length cell input from the asynchronous transfer mode bus into compressed and encoded voice data, an outputs the data to the voice compressing coder-decoder circuit.
With this configuration, the voice data for each channel can be compressed, encoded, and mapped to a fixed-length cell only by connecting the hybrid process package device of an appropriate scale to the purpose to the asynchronous transfer mode bus slot and the time-division multiplexing bus slot (and control bus slot).
Since the no-voice detection information for stopping data from being put in a cell in the no-voice period detected by the voice compressing coder-decoder circuit can be easily transmitted to the cell assembly/disassembly layer terminating circuit in the same package device, the control process can be prevented from becoming too complicated.
Finally, as an extended configuration according to the present invention, one fixed-length cell data time-division data hybrid multiplexing device or a fixed-length cell data processing device (1502) for exclusively processing fixed-length cell data, and another one or more fixed-length cell data/time-division data hybrid multiplexing devices (1501) can be designed to be interconnected by an asynchronous transfer mode line (ATM exclusive line 1503) for transmitting fixed-length cell data through an asynchronous transfer mode line port package device (line port 309) connected to an asynchronous transfer mode bus slot in each of the fixed-length cell data/time-division data hybrid multiplexing devices.
With the above described extended configuration, the functions can be easily improved stepwise, the devices can be quickly connected, the number of lines of connected signals can be reduced, and each device can be remotely provided.
In this case, the asynchronous transfer mode buses of the devices are connected through the asynchronous transfer mode interface. The communications of the control information between the devices can be easily realized by the standardized asynchronous transfer mode interface. Therefore, the control process can be prevented from becoming too complicated.